Description

Cancer

Description

CI-1040 (PD 184352) is an ATP non-competitive MEK1/2 inhibitor with IC50 of 17 nM.

Targets

IC₅₀

In Vitro

CI-1040 treatment produces a reduction of pMAPK levels in multiple tumor cells including Colon 26, BX-PC3 pancreatic, A431 cervical, HT-29 colon, ZR-25-1 breast and SKOV-3 ovarian carcinomas. CI-1040 treatment doesn’t inhibit the phosphorylation of Jun kinase, p38 kinase or Akt, indicating CI-1040 specifically targets MEK. Inhibition of MAPK activation by CI-1040 prevents cell cycle progression and induces a G1 block. ^[1] The IC50 for inhibition of MEK1 by CI-1040 is 0.3 uM, 15-fold higher than the concentration required to inhibit the EGF-induced activation of ERK2 in Swiss 3T3 cells. These results indicate CI-1040 exerts its effects on cells by suppressing the activation of MKK1, and not by blocking its activity. 2 nM PD184352 inhibits the activation of MKK1 in Swiss 3T3 cells by 50%, while over 100-fold concentration of CI-1040 inhibits MEK1 in vitro. PD184352 also inhibits the Raf-catalysed phosphorylation of MEK1 without any effect on the Raf-catalysed phosphorylation of myelin basic protein. ^[2] CI-1040 inhibits 86% of papillary thyroid carcinoma (PTC) cell growth with the RET/PTC1 rearrangement at 10μM compared with cells treated with DMSO only. CI-1040 shows potent inhibition to PTC cells (BRAF mutation) with GI50 of 52 nM, but low activity to RET/PTC1 rearrangement type with GI50 of 1.1μM. ^[3] A recent research indicates CI-1040 increases the apoptotic effect of BMS-214662 in a CML blast crisis cell line, K562, and in primary chronic phase CD34+ CML cells. ^[4]

In Vivo

Oral dosing of CI-1040 impairs the growth of colon tumor xenografts of mouse and human with a wide dose range of 48-200 mg/kg per dose, but not of P388 leukemia. ^[1] CI-1040 inhibits the tumor xenografts from PTC cells carrying a BRAF mutation with 31.3% reduction, carrying the RET/PTC1 rearrangement with 47.5% reduction than in untreated (vehicle) mice after 3 weeks of oral administration (300 mg/kg/d). No toxic effects are observed in any mice when they are treated with CI-1040. ^[2] Transient exposure of mammary tumors to CI-1040 and UCN-01 causes tumor cell death in vivo and prolonged suppression of tumor regrowth. Combined treatment with CI-1040 (25 mg/kg) and UCN-01 (0.1-0.2 mg/kg) significantly reduces MDA-MB-231, and largely abolishs MCF7 tumor growth in implanted athymic mice, while either single treatment has no significant activity. The drug combination leads to profound tumor cell death which correlates with a reduction in the phosphorylation of ERK1/2 and the immuno-reactivity of Ki67 and of CD31. ^[5]

Clinical Trials

Currently under Phase II in breast cancer, colorectal cancer, lung cancer, and pancreatic cancer.

Features

First MEK inhibitor to begin clinical development.

Description

CI-1040 in combination with mTOR inhibitor, Rapamycin, exhibits dose-dependent synergism in human lung cancer cell lines that is associated with suppression of proliferation rahter than enhancement of cell death. ^[6] Combination of CI-1040 and Sorafenib synergistically inhibited ERK phosphorylation and cell growth and induced apoptosis in both HCC cells and HUVECs. Combination therapy inhibited tumor growth significantly better than either single agent in the xenograft models. ^[7] Combination of CI-1040 with Gefitinib effectively results in inhibition of the MAPK signaling pathway and exerts antitumor effects in vitro and in vivo in tumors resistant to each of the agents alone. Combined treatment in four tumor xenografts generated from patients with resected pancreatic cancer shows more effective than either single agent alone in this model. ^[8]

MEK1 Assay

MAP kinase is activated after phosphorylation by MEK; the activated MAP kinase subsequently phosphorylates myelin basic protein (MBP).Incorporation of ³²P into myelin basic protein (MBP) is assayed in the presence of glutathione S-transferase (GST) fusion proteins containing the 44-kDa MAPK (GST-MAPK) or the 45-kDa MEK (GST-MEK1). Assays are conducted in 50μL of 50 mM Tris, pH 7.4/10 mM MgCl ₂ /2 mM EGTA/10 μM [γ-³²P]ATP containing 10 μg of GST-MEK1, 0.5 μg of GST-MAPK, and 40 μg of MBP. After incubation at 30°C for 15 minutes, reactions are stopped by addition of Laemmli SDS sample buffer. Phosphorylated MBP is resolved by SDS/10% PAGE. This screening effort leads to the discovery of several small-molecule inhibitors of MEK, i.e. CI-1040. Experiments assessing the order of addition shows that CI-1040 directly inhibits MEK1 with a 50% inhibitory concentration (IC50) of 17 nM, without affecting the activity of MAPK.

Cell Lines

Colon 26 carcinoma cells

Concentrations

0.1-10 μM

Incubation Time

24 hours

Methods

Cells are planted seeded in T-75 cm ² flasks and treated the next day for 24 hous with either DMSO or CI-1040. Single-cell suspensions are collected, and pellets are fixed in ice-cold ethanol (70%) for 30 minutes. After centrifugation of the samples, propidium iodide (50 μg/mL) and RNase (30 units/mL) are added to the pellets for 20 minutes at 37 °C. After filtration, samples are analyzed by flow cytometry.

Animal Models

PTC cells in athymic mice

Formulation

Cremophor EL–95% ethanol (50:50) and dilutes with water

Doses

150 mg/kg

Administration

Orally twice daily via p.o.